The technique of the present invention is applicable to a variety of systems for forming fiber mats, particularly where the mat is formed on a perforated fiber-collecting conveyor. One of the most widely used techniques of this type comprises a system especially adapted to the formation of glass fiber mats by centrifugally and radially projecting molten streams of the attenuable mineral material, especially molten glass, the molten streams being subjected to the attenuating action of a hot attenuating blast directed into the path of the centrifugally-projected streams, to thereby attenuate the streams to form fibers while the streams are in the molten or attenuable state. In this type of well-known fiber producing technique, the attenuated fibers are entrained in the attenuating gas blast, and the fiber-laden blast is exposed to the surrounding atmosphere, and in consequence, air is induced into the flow, thereby producing what is commonly referred to as a fiber-laden gas current. This current is directed against the surface of a perforated fiber-collecting conveyor, thereby resulting in passage of the gas of the current through the conveyor and depositing of the fibers on the conveyor surface.
It is also customary in an installation of the kind just referred to to subject the fiber-laden gas current to the spraying of liquids, especially a fiber binder material commonly comprising a thermosetting binder material which, when cured and solidified in the mat of fibers acts to stabilize the mat and provide an integrated, readily handleable fibrous mat. The perforated conveyor employed for the above purpose also delivers the formed mat to a curing oven in which the mat is subjected to heating for the purpose of setting or curing the binder or binding agent initially applied to the fibers when being carried by the fiber-laden gas current above-referred to.
As above-indicated, although the technique of the present invention is applicable to a wide variety of fiberization and mat-forming operations, the invention is particularly well-suited to use in a system of the kind referred to and therefore in the following description and also in the accompanying drawings, the features of the invention are disclosed as applied to a fiberization and mat-forming technique of the kind briefly described above.
In order to accomplish a number of improvements in the mat formation, the present invention provides a technique for withdrawing a peripheral portion of the fiber-laden gas current, this withdrawal being effected at a point downstream of the fiber attenuation zone and upstream of the depositing of the fibers from the gas-laden current upon the perforated conveyor. Several desirable objectives are achieved by this peripheral withdrawal of a portion of the fiber-laden gas current. One of these objectives is to reduce the compacting action resulting from directing of the fiber-laden current against the perforated fiber-collecting conveyor, and in consequence of this reduction, the mat is of lower density while being carried by the conveyor. Subsequently the mat may be fed between conveyors in a curing oven in which the desired dimensions and compacting may be more precisely established.
Another objective is achieved by locating the gas withdrawal equipment at a point intermediate the zone where attenuation occurs and the zone where the binder spray is applied to the fibers in the fiber-laden gas current. By withdrawing a peripheral portion of the fiber-laden current intermediate the attenuation and the application of the binder, the temperature of the current is reduced in the region downstream of the application of the binder and also from that zone downstream to the perforated conveyor. In consequence of this, the tendency for the thermosetting binder to be prematurely hardened while the mat is on the conveyor is reduced.
The foregoing and numerous other objectives and advantages will appear more clearly after consideration of the accompanying drawings and the following description of those drawings.